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For lamp filaments. | Atomic Number: | 74 | Atomic Symbol: | W | | Atomic Weight: | 183.5 | Electron Configuration: | 2-8-18-32-12-2 | | Shells: | 2,8,18,32,12,2 | Filling Orbital: | 5d4 | | Melting Point: | 3410oC | Boiling Point: | 5927oC | | Description: | Hard, silver-white metal. | | Uses: | Used widely in the electronics industry. Made into filaments for
vacuum tubes
and electric lights. Also as contact points in cars.
Combined with
calcium or magnesium it makes phosphors |
History(Swedish, tung sten, heavy stone) In 1779 Peter Woulfe examined
the mineral now known as wolframite and concluded it must contain a new
substance. Scheele, in 1781, found that a new acid could be made from tungsten
(a name first applied about 1758 to a mineral now known as scheelite). Scheele
and Berman suggested the possibility of obtaining a new metal by reducing this
acid. The de Elhuyar brothers found in acid in wolframite in 1783 that was
identical to the acid of tungsten (tungstic acid) of Scheele, and in that year
they succeeded in obtaining the element by reduction of this acid with charcoal.
Occurence- Tungsten occurs in wolframite, scheelite, huebnertie, and ferberite.
- Important deposits of tungsten occur in California, Colorado, South Korea,
bolivia, Russia, and Portugal.
- China is reported to have about 75% of the world's tungsten resources.
IsotopesNatural tungsten contains five stable isotopes. Twenty one
other unstable isotopes are recognized.
Properties- The metal is obtained commercially be recucing tungsten oxide with hydrogen
or carbon.
- Pure tungsten is a stelel-gray to tin-white metal.
- Very pure tungsten can be cut with a hacksaw, and can be forged, spun,
drawn, and extruded.
- The impure metal is brittle and can be worked only with difficulty.
- Tungsten has the highest melting point of all metals, and at temperatures
over 1650C has the highest tensile strength.
- The metal oxidizes in air and must be protected at elevated temperatures.
- It has excellent corrosion resistance and is attacked only slightly by most
mineral acids.
Uses- The thermal expansion is about the same as borosilicate glass, which makes
the metal useful for glass-to-metal seals.
- Tungsten and its alloys are used extensively for filaments for electric
lamps, electron and television tubes, and for metal evaporation work; for
electrical contact points for automobile distributors; X-ray targets; windings
and heating elements for electrical furnaces; and for numerous spacecraft and
high-temperature applications.
- High-speed tool steels, Hastelloy??, Stellite??, and
many other alloys contain tungsten.
- Tungsten carbide is of great importance to the metal-working, mining, and
petroleum industries.
- Calcium and magnesium tungstates are widely used in fluorescent lighting;
other salts of tungsten are used in the chemical and tanning industries.
- Tungsten disulfide is a dry, high-temperature lubricant, stable to 500C.
- Tungsten bronzes and other tungsten compounds are used in paints.
CostsTungsten powder (99.9%) costs about $50/lb.
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